This invention relates to a novel very high-pressure hose with high dynamic endurance, the hose being strengthened by synthetic fibre filaments and being of use to carry fuels, gases and hydraulic fluids.
High-pressure hoses comprising a tube covered by an axial outer cylindrical element produced by braiding a number of filaments are known. Each set of filaments is wound spirally on the tube. For example, metal wires having a diameter of from 0.3 to 0.6 mm are used for braiding. However, the wires, since they are placed spirally on the tube by braiding, experience alternate bending when used at very high pressure and this alternate bending may break the wires. Also, since braiding bends the wires, with the possible result of them breaking and of the inner tube being perforated, it is preferred to layer filaments placed one above another.
To ensure that the hose is strong enough to carry high-pressure fluids, efforts have been made to minimise the gap in the braided element between the layers of braided metal wires. Layers of coplanar steel wires do not allow adequate filling and holes and voids remain between two contiguous layers, with the result that the hose has less strength to withstand high pressures. Improvements have been made to the conventional braiding of steel wires in coplanar layers and groups of non-coplanar fine wires have been braided to provide better filling (French patent specification 1 522 053). Unfortunately, the resulting hoses are heavy since the amount of material placed on the central tube is greater when groups of fine wires are braided than when layers of wires are braided.
It is the object of the invention to obviate these disadvantages.
It is a first object of the invention to provide hoses comprising a central tube covered by braided synthetic fibre filaments, the braiding providing a gapless covering surface and thus making it possible to provide the hose with very good high-pressure strength.
It is a second object of the invention to provide hoses having a long working life in respect or mechanical stresses and without any limitation of the materials used for the hoses.
It is a third object of the invention to provide hoses which for a given strengths are lighter than the known hoses and which are not fatigued by alternate bending and which withstand corrosion, abrasion, heat, chemical agents and ultraviolet radiation.
The invention accordingly relates to a hose comprising an inner plastic tube covered by a braiding of filaments disposed in helically crossed layers around the inner tube, the hose being such that the filaments are made of plastic and are so deformed in their right cross-section that the gap between any two adjacent layers which extend in the same direction so one another is at least 100% filled.
Preferably, the plastic is aromatic polyamide such as KEVLAR or TWARON, the registered trade marks of the Du Pont de Nemours and Enka companies respectively.
The invention also relates to a process for producing such a hose.